Kerry has been dutifully playing attack ads in a similar strategy, but the problem is that he hasn't defined himself, to offer a counter-narrative to the Bush one. This article in the WaPo takes Kerry to task on these grounds:
As the general election begins and Democrats play to a broader audience, Kerry is under pressure to define himself clearly and to offer voters a post-Clinton blueprint for a Democratic presidency.
"My greatest worry about the Kerry candidacy is that the competence and confidence it's demonstrated early on in rapid reaction to news of the day will come at the expense of an organized and systematic effort to tell the American people what John Kerry would do as president of the United States," said William Galston, a University of Maryland professor and former Clinton domestic adviser. "By the end of the campaign, if people can't spontaneously name two or three things that are big things that he would do differently, then I think the campaign will not have succeeded in getting across the whole message."
I tend to agree with Ezra that Kerry needs to delegate defending himself against the Bush attacks to a "shadow cabinet" of prominent Democrats. The advantage of this is that it frees Kerry to entirely focus on what he would do / why a Kerry Presidency would be different, and thus rise above the partisan pray (just as Bush has done). After all, there's only one Kerry with finite time to campaign, so his time is better spent on the positive and leaving the negative to surrogates.